Despite its cute but clunky looks, those who helped design it say Curiosity is surprisingly rugged. Given where it’s going, a planet with an average temperature of -81 degrees Fahrenheit and a surface strewn with rocks, it will need all the ruggedness it can get.

ASTRONOMER CARL SAGAN called Mars “a kind of mythic arena, onto which we have projected our Earthly hopes and fears.” Curiosity’s lead scientist knows all too well of what Sagan spoke. In 2001, Grotzinger was a professor at the Massachusetts Institute of Technology when he wrote a proposal to NASA to become a participating scientist on the agency’s Spirit and Opportunity rover missions to Mars. “I thought, you know, Mars—what do I know about Mars?” he says. “I’ll have fun for three months, then the rover will die, and I’ll go back to what I was doing.”

NASA hired him. Opportunity, tasked with assessing the history of water on Mars, touched down and began beaming back pictures of banded rock outcroppings that looked stunningly familiar to Grotzinger. He’d seen comparable formations while working with very old rocks on Earth, where evidence of prehistoric organic life is rare. The photographs left him awestruck.

“Every day a new image would arrive,” he says. “You knew you were the only person in the solar system looking at it, and yet you saw so many things that were similar to Earth. It was one of the most intense experiences of my life.”

Curiosity’s landing zone, in Mars’ Gale Crater, features a series of rock layers that satellite reconnaissance photos indicate are collectively three times as tall as the Grand Canyon is deep. Grotzinger and his scientific team hope that by scrutinizing each layer, from bottom to top, they will learn how Mars evolved. “It’s like reading a novel,” says Grotzinger. “The layers at the bottom are the first chapters of the book, and the layers at the top are the last chapters. We don’t know what exactly the story’s going to be, but we know it’s going to be a good one because we have lots of chapters.”

Assuming, of course, Curiosity makes it to page one.

When Spirit and Opportunity came hurtling down, they were cocooned in airbags, bouncing onto Mars like so many bunches of steroidal grapes. Not Curiosity. Here’s the plan: The spacecraft carrying it enters Mars’ atmosphere at about 13,200 mph. If all goes well, the rover touches down about seven minutes later. But whether it alights upon Mars like a butterfly or crashes kamikaze-style depends on an elaborate sequence of computer-controlled procedures going right. The landing, in other words, is now beyond JPL’s control. No wonder it has come to be known among the lab’s engineers and scientists as the Seven Minutes of Terror (see “How Things Work: Dropping in on Mars,” Dec. 2011/Jan. 2012).

Because Curiosity is too heavy to land on airbags, it will descend via what JPL calls a “sky crane maneuver,” in which the rover dangles below the hovering, thruster-controlled descent stage. When Curiosity senses touchdown approaching, the bridle suspending it automatically releases, and the descent stage zooms off to crash several hundred feet away. At this point, it will take the team 14 minutes—the time required for a signal from Curiosity to reach Pasadena—to know if the rover is good to go.

“We’re either gonna be really happy or really sad,” says Chris Leger, 38, a tousled-hair surfer who used to play in a funk band before picking up a doctorate from Carnegie Mellon and going to work at JPL as a software engineer.

On the day I visited, the potential for catastrophe seemed as far away as Mars itself. Leger and robotics engineer Curtis Cullins, 45, were busy inside JPL’s three-story In Situ Instrument Laboratory, manipulating the robotic arm of Curiosity’s stunt double, which hunkered on a testbed of crushed garnet, intended to replicate the parched, gritty surface of Mars.